This invention relates to improvements in methods of and in apparatus for pivotally coupling stacked sheet-like commodities with each other. For example, the method and the apparatus of the present invention can be utilized to convert stacks of paper sheets, plastic foils, cardboard panels, metallic foils and/or the like (hereinafter called sheets for short) into memo pads, other types of pads, calendars, advertising brochures or the like (hereinafter called commodities) by resorting to elongated connectors having rows of preferably arcuate tines or prongs which can be introduced into the rows of perforations provided in the individual sheets at the spines of stacks of overlapping sheets.
As a rule, or at least in many instances, the connectors which are utilized to pivotably connect the sheets of a stack of overlapping sheets comprise (a) coil springs or (b) elongated connectors having a first row of substantially C-shaped tines or prongs and a second row of tines or prongs which are exact or at least substantial mirror images of the tines or prongs of the first row, wherein the tines or prongs of the first and second rows are bend and closed together when being received in corresponding perforations of a stack of overlapping sheets. Each hole consists of a plurality of at least substantially registering perforations provided in each of the overlapping sheets. The present invention relates to a method of and to an apparatus for pivotally connecting overlapping sheets of stacks by resorting to connectors of the type described at (b) hereinbefore. The prongs of the substantially omega-shaped connectors can consist of a metallic or a plastic material.
Apparatus for converting the aforementioned omega-shaped connectors and stacks of sheets into pads or analogous commodities normally or often form part of semi-automatic or fully automated production lines which employ facilities for converting large panes or webs or strips of paper or the like into stacks of overlapping sheets, for providing the sheets with perforations preparatory to, during or subsequent to stacking, for providing (if necessary) some or all of the sheets with printed matter and/or other form(s) of information, and for pivotably coupling the sheets of each stack to each other by substantially omega-shaped connectors. Accurate overlapping of sheets in each stack prior to the application of connectors is not only desirable but actually critical because this facilitates accurate, predictable and rapid introduction of tines or prongs into the respective holes and the conversion of stacks into pads or analogous commodities of satisfactory utility and eye-pleasing appearance. When the insertion of the tines or prongs (hereinafter called prongs) into the respective holes in the spine of a stack of overlapping sheets is completed, each prong of one row cooperates with one prong of the other row to form therewith a substantially O-shaped composite prong or eyelet which allows each individual sheet or a group of two or more neighboring sheets of the finished commodity to pivot relative to the other sheet(s) of the stack. Prior to the deformation of its prongs, each connector resembles an elongated worm-like larva (such as a caterpillar) having two mirror symmetrical sets of legs (prongs) each of which can resemble a part of a circle (i.e., a letter C) extending along an arc of approximately 180°. The connectors are mass-produced in a machine which turns out so-called “open” connectors, i.e., each of the prongs which form the two sets of prongs has a first end portion of one piece with the elongated bridge and a second end portion. The second end portions of prongs in one of the rows are spaced apart from the second end portions of prongs in the other row. When the connector is properly inserted into a stack and its prongs are properly deformed, the second end portion of each prong of one of the rows can abut or overlie the second end portion of the corresponding prong of the other row, and such second end portions of each pair of C-shaped prongs can be confined in the respective hole in the spine of the corresponding stack.
The manner in which the shapes of holes in the spines of stacked sheets can be altered prior to insertion of portions of connectors is disclosed in commonly owned copending U.S. patent application Ser. No. 10/400,065 filed Mar. 27, 2003 by Ferdinand Fuchs for “METHOD OF AND APPARATUS FOR GATHERING STACKS OF SHEETS AND THE LIKE”.
Apparatus for pivotally connecting stacked sheets to each other by spiral-shaped connectors is disclosed in commonly owned copending patent application Ser. No. 10/396,705 filed Mar. 26, 2003 by Ferdinand Fuchs for “APPARATUS FOR COUPLING STACKED SHEETS”.